It is well known that ultra-violet ("UV") radiation in the 210 to 315 nanometer range may cause corneal damage. Thus, ocular devices containing UV absorbers are desirable and methods for their production are known.
Most known UV absorbers used in ocular devices are incorporated into the polymer matrix forming the device by copolymerization of the monomers forming the device with a functionalized form of UV absorber. The majority of commercially available ocular devices, particularly contact lenses, are manufactured using free radical-polymerization processes. The most convenient method of carrying out these polymerizations is by irradiation with UV light.
Unfortunately, when UV light irradiation is used in the presence of the UV absorber, the UV absorbing functional group or groups of the absorber interferes with curing in that the functional group competes with the UV photoinitiator used in the polymerization for the incident light. The result is that the polymerization process is less efficient and may produce undercured products. Although changes in the polymerization process, such as the use of visible light initiators, may be made, these changes generally make the polymerization less efficient.
Thus, a need exists for a method for providing an efficient process for producing ocular devices containing UV absorbers using a UV initiated polymerization processes.